While you may wonder/think that Google uses git and various fashionable methods interacting with a distributed version control system, they do not!

Here is a great explanation of what Google does regarding source control and more importantly: why they do it this way

Source: https://trunkbaseddevelopment.com/game-changers/

Continuing on this train of thought: What would you use when you want to centralize all the code into 1 repo? Google ditched Perforce over something they developed themselves. While fun and challenging: not an option for us mere mortals.

Perhaps Microsoft comes to the rescue? The ‘New Microsoft’ says they are very pro-open-source and they tried to solve some of the problems with massive git repos by developing GVFS